The preferred embodiment of the present invention generally relates to improvements in an internal imaging probe, and more particularly relates to a transesophageal ultrasound probe with an imaging element position sensor positioned within the scanhead of the probe to detect the position of an imaging element located within the scanhead.
Various medical conditions affect internal organs and structures. Efficient diagnosis and treatment of these conditions typically require a physician to directly observe a patients internal organs and structures. For example, diagnosis of various heart ailments often requires a cardiologist to directly observe affected areas of a patients heart. Instead of more intrusive surgical techniques, ultrasound imaging is often utilized to directly observe images of a patients internal organs and structures.
Transesophageal Echocardiography (TEE) is one approach to observing a patients heart through the use of an ultrasound transducer. TEE typically includes a probe, a processing unit, and a monitor. The probe is connected to the processing unit which in turn is connected to the monitor. In operation, the processing unit sends a triggering signal to the probe. The probe then emits ultrasonic signals into the patients heart. The probe then detects echoes of the previously emitted ultrasonic signals. Then, the probe sends the detected signals to the processing unit which converts the signals into images. The images are then displayed on the monitor. The probe typically includes a semi-flexible endoscope that includes a transducer located near the end of the endoscope. Typically, the transducer is a piezoelectric transducer having 48 to 96 piezoelectric elements.
Typically, during TEE, the endoscope is introduced into the mouth of a patient and positioned in the patients esophagus. The endoscope is then positioned so that the transducer is in a position to facilitate heart imaging. That is, the endoscope is positioned so that the heart or other internal structure to be imaged is in the direction of view of the transducer. Typically, the transducer sends ultrasonic signals through the esophageal wall; the ultrasonic signals come into contact with the heart or other internal structures. The transducer then receives the ultrasonic signals as the ultrasonic signals bounce back from various points within the internal structures of the patient. The transducer then sends the received signals back through the endoscope typically via wiring. After the signals travel through the endoscope, the signals enter the processing unit, typically via wires connecting the endoscope to the processing unit.
Occasionally, the transducer may be rotated about an axis perpendicular to its imaging surface. The transducer may be rotated to change the imaging scan-plane during the imaging process. That is, the transducer may be rotated to image the internal structure from a horizontal scan-plane or a vertical scan-plane (and all positions in between). Typically, the transducer may be rotated 90xc2x0 in either direction from its normal position.
The position, or orientation, of the transducer is typically measured by a position sensor, such as a potentiometer, located within the control handle of the probe. A mechanical transfer mechanism connects the position sensor located in the control handle to the transducer located in the scanhead. For example, the transducer may be connected to the position sensor via a flexible axle or shaft. Thus, the transducer and the position sensor are typically separated by a significant distance. The separation of the transducer and the position sensor may cause errors in the position measurement. For example, mechanical imperfections, such as slack, spring tension, mechanical hysteresis, or dead zones, may occur due to the extended mechanical distance between the transducer in the scanhead and the position sensor in the control handle. The mechanical imperfections may lead to inaccurate position measurement. The position measurement inaccuracies may lead a physician, or other operator of the probe, to believe that the physician is viewing an internal structure from a scan plane other than the scan plane actually being viewed. For example, the position sensor may measure the position of the transducer at a position 33xc2x0 from the normal orientation of the transducer when the correct measurement is 30xc2x0 from the normal orientation. Typically, the position of the transducer measured by the position sensor in the control handle is then displayed on the monitor of the imaging system. Consequently, the physician may misdiagnose and/or mistreat the patient who is being imaged if the deviation is great enough, for example a 10xc2x0 deviation. Further, smaller errors and deviations, such as a deviation between 3xc2x0-5xc2x0, typically cause inaccuracies when two-dimensional images are combined to form three-dimensional images.
While the transducer typically images an internal structure in two dimensions, the two-dimensional images may be recorded and combined to produce three-dimensional images. In order to produce three-dimensional images, the transducer is typically rotated through various radial angles thereby imaging various scan-planes. The images from the various scan-planes are recorded and combined using corresponding recorded position measurements. However, inaccuracies in position measurement may skew the resulting three-dimensional images. Further, accurate position measurements are necessary to produce the desired accurate three-dimensional images.
Therefore, a need exists for a more accurate system and method for measuring the position of an imaging element, such as a transducer, within an imaging probe. Specifically, a need exists for an imaging system that provides more accurate measurement of the position of a transducer within a transesophageal ultrasound probe. Additionally, a need exists for an imaging system that provides more accurate measurement of the position of a transducer within an imaging probe to assist in producing accurate three-dimensional images.
The present invention relates to an imaging probe, such as a transesophageal ultrasound probe, for use in a medical imaging system and/or a three-dimensional imaging system. The probe includes an articulating portion having a scanhead. The scanhead includes an imaging element, such as a transducer, and a position sensor positioned within the scanhead. Preferably, the imaging element is connected to the position sensor via an axle. Therefore, the imaging element and the position sensor rotate in the same direction and at the same rate as one another. That is, the rotation of the imaging element and the position sensor is synchronized. The location of the position sensor within the scanhead provides accurate measurement of the position of the imaging element.
The position sensor preferably includes a code disk having apertures and a system of light emitters and detectors. As the code disk rotates in synchronization with the imaging element, the pattern of detection of light through the apertures measures the position of the imaging element. Various alternative position sensors, such as potentiometers, may be utilized with the imaging element. The probe also includes a control handle having imaging and articulation controls.